CO2-switchable dispersion of a natural chitosan and its application as a responsive pickering emulsifier
2018
Ren, Dongyin | Xu, Shengming | Sun, Dejun | Wang, Qibao | Xu, Zhenghe
The natural chitosan aggregates obtained by increasing the pH of aqueous solutions are found to be responsive to CO₂/N₂ switching. These chitosan aggregates can be dispersed in water upon CO₂ bubbling and precipitated out with N₂ bubbling at room temperature. Liquid paraffin-in-water Pickering emulsions are prepared using these aggregates as the stabilizer. These emulsions can be demulsified completely with CO₂ bubbling, and the separated two phases can be re-emulsified with N₂ bubbling under mechanical mixing. This CO₂/N₂-switched demulsification/re-emulsification cycle can be repeated several times. The CO₂/N₂-switched dispersion/aggregation of the chitosan aggregates leads to desorption/adsorption of the aggregates at the oil/water interface and hence the disappearance/reconstruction of the three-dimensional network structure of the aggregates, which is responsible for the demulsification/re-emulsification. Experimental evidence including the measurement of interfacial tension, interfacial dilatational elastic modulus and rheological properties, and micrographs of formed emulsions is given to support the proposed stabilization mechanism.
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